1. Field of the Invention
The present invention relates to a waterproof gasket which is installed to an outer shell case of a small size electronic appliance such as a mobile device, a digital camera or the like.
2. Description of the Conventional Art
An outer shell case of a mobile device such as a cellular phone or the like is structured such that a waterproof gasket 100 as shown in FIG. 6 is interposed between mating faces in a division portion, whereby a waterproofing is achieved. This kind of waterproof gasket 100 is made of a rubber-like elastic material (a rubber material or a synthetic resin material having a rubber-like elasticity), and is formed as an endless shape which has straight portions 101a and corner portions 101b alternately in a peripheral direction, for example, extends in a rounded rectangular shape, in correspondence to a shape of the mating face in a division portion of the outer shell case.
Further, this kind of waterproof gasket 100 has a chevron main seal portion 101 and a plurality of seat seal portions 102 in an opposite side thereto, as shown in FIG. 7, is retained within a gasket retention groove 201a which is formed in one case member (for example, a case main body) 201 constructing the outer shell case along its outer periphery, and is structured such that the main seal portion 101 is brought into close contact with another case member (for example, a front panel) 202 and the seat seal portion 102 is seated in a close contact state on a bottom surface of the gasket retention groove 201a, in an assembled state of the outer shell case, thereby achieving a sealing function with respect to a dust, a water or the like in an outer portion.
Further, since a sealing performance is damaged and a water intrusion from an outer portion is generated even under a slight water pressure if the waterproof gasket 100 collapses within the gasket retention groove 201a in an assembling process of the outer shell case (the case member 201 and the case member 202) or the like, there has been conventionally known that the waterproof gasket 100 has a shoulder portion 103 for preventing the collapsing that is circumferentially continuously formed in a protruding manner in both side surface portions between the main seal portion 101 and the seat seal portion 102 as shown in the Japanese Unexamined Patent Publication No. 2008-249139.